He shoots at the bird - a redstart (6)
I believe the answer is:
sniper
'he shoots' is the definition.
'the bird a redstart' is the wordplay.
'the bird' becomes 'snipe' (snipe is a kind of bird).
'a redstart' becomes 'r' (start of the word 'red').
'snipe'+'r'='SNIPER'
'at' is the link.
(Other definitions for sniper that I've seen before include "Military marksman" , "Hidden sharpshooter" , "Hidden gunman" , "He shoots from hiding-place" , "Hidden marksman" .)